A lot of high school and even college students are taught that the historical period roughly from the fall of Rome to the 15th century was a time of intellectual stagnation with little or no scientific or technological progress.
The ignorance that descended over Europe during this epoch has caused it to be called the "Dark Ages," a pejorative assigned to the Middle Ages by historians of the 18th century hostile to the Church and desirous of deprecating the period during which the Church wielded substantial political power.
Lately, however, historians have challenged the view that this epoch was an age of unenlightened ignorance. Rodney Stark has written in several of his books (particularly, his How the West Won) of the numerous discoveries and advancements made during the "dark ages" and concludes that they weren't "dark" at all.
The notion that they were, he argues, is an ahistorical myth. Indeed, it was during this allegedly benighted era that Europe made the great technological and philosophical leaps that put it well in advance of the rest of the world.
For example, agricultural technology soared during this period. Advances in the design of the plow, harnessing of horses and oxen, horseshoes, crop rotation, water and wind mills, all made it possible for the average person to be well-fed for the first time in history.
Transportation also improved which enabled people and goods to move more freely to markets and elsewhere. Carts, for example, were built with swivel axles, ships were more capacious and more stable, and horses were bred to serve as draught animals.
Military technology also made advances. The stirrup, pommel saddle, longbow, crossbow, armor, and chain mail eventually made medieval Europeans almost invincible against non-European foes.
Similar stories could be told concerning science, philosophy, music and art, and thus the view espoused by Stark that the medieval era was a time of cultural richness is gaining traction among contemporary historians who see the evidence for this interpretation of the time to be too compelling to be ignored.
This short video featuring Anthony Esolen provides a nice summary: